> would it even work on an MMO?

CheatEngine is a great first step in developing any bot, for any game.

GW2 doesn't have to trust the client for CE to be useful, it's just that the usefulness is different than what you're using it for currently. The goal of CE in developing an MMO bot is to figure out where in memory things like player location, party members, linked list of all nearby objects, etc, are. This allows the user to write the bot in a way that's pulling information directly from memory. CE is a great way to back into this data (coupled with a debugger/disassemble, of course).